1. Field of the Invention
The present invention relates to an absorbent article, such as a sanitary napkin, a panty liner and a pad for incontinence, and in particular, it relates to an absorbent article in that absorbent property and diffusion property between a surface sheet and an absorbent core are improved to have excellent dry feeling.
2. Description of the Related Art
There have been some absorbent articles including a sanitary napkin and a panty liner in which a skin contacting surface of a surface sheet is of a corrugated configuration to have peaks and valleys alternately arranged so that the surface sheet to contact the skin directly is improved in dry feeling and soft feeling.
However, when the direction along which the peaks and valleys extend (i.e., an orientation direction) is identical with the longitudinal direction of the absorbent article, the corrugated configuration is liable to be resistance against the absorbent article being incurvated in the longitudinal direction. Accordingly, in order to incurvate and deform the absorbent article by pressure from the body upon use, a plurality of creases are necessarily formed on the surface of the peaks to extend in the transverse direction perpendicular to the longitudinal direction. Because the surface sheet is folded at the creases, the surface sheet can be incurvated along the body shape of the user.
In the parts of the surface sheet where the creases are formed, the surface sheet is in contact with the absorbent core located therebelow, but in the parts where the creases are not formed, an excessive force may be applied to separate the absorbent core and the surface sheet. As a result, in the part where the absorbent core and the surface sheet are separated, the amount of liquid remaining in the surface sheet is increased, so that the surface sheet loses dry feeling and provides the user with uncomfortable wet feeling.
In particular, because the pressure from the body does not act uniformly on the whole surface of the surface sheet, the surface sheet is often incurvated with irregular curvature radii. That is, in parts where the pressure from the body is concentrated, the curvature radius becomes small to form a large number of creases, whereas in parts where the pressure from the body acts relatively lightly, the curvature radius becomes large to decrease the number of the creases.
Furthermore, because the peaks and valleys are liable to be irregularly creased, there are cases where the peak plugs the valley, and the flow of an excreted liquid is dammed at a part where the surface sheet is bent at an acute angle.
As described in the foregoing, when creases are irregularly formed on the surface sheet, the part where the surface sheet and the absorbent core are separated and the part where the surface sheet is bent are formed irregularly, and therefore an excreted liquid is insufficiently diffused to cause a problem that the surface sheet has a part exhibiting dry feeling and a part exhibiting no dry feeling.
An object of the invention is to provide an absorbent article in which a surface sheet can be easily incurvated as a whole so that absorbent property and diffusion property between the surface sheet and an absorbent core are improved to have excellent dry feeling.
According to the invention, there is provided an absorbent article comprising an absorbent layer and a liquid-permeable surface sheet placed on a liquid-receiving side of the absorbent layer for introducing excreted liquid from the human body to the absorbent layer, the surface sheet being of a corrugated configuration to have valleys and peaks extending in a longitudinal direction of the article and alternately arranged in a transverse direction perpendicular to the longitudinal direction, wherein
each peak is formed with sparse parts and dense parts alternately arranged in the longitudinal direction, and the surface sheet has a lower fiber density in the sparse parts than in the dense parts.
For example, the dense parts may be formed by compressing the peaks intermittently in the longitudinal direction, so that parts that do not receive the compression between the dense parts are the sparse parts.
It is preferred that the peak is made uneven at the top thereof so that the sparse parts form recessed parts and the dense parts form raised parts.
In the invention, the peaks of the corrugated surface sheet can be easily bent due to the presence of the sparse parts having a low fiber density. In addition, because the sparse parts are formed along the peaks of the corrugated surface sheet, the surface sheet can be incurvated as a whole by bending each peak at the sparse parts. Therefore, the peaks are not forcibly bent at the dense parts, so that the surface sheet and the absorbent core are prevented from locally separating by an excessive force. As a result, the liquid permeability of the surface sheet and the absorbent core can be prevented from lowering, and an excreted liquid received by the surface sheet can be effectively led to the absorbent core.
If the sparse parts are recessed toward the absorbent core (i.e., lowered than the dense part), the peaks can be bent at the sparse parts more easily.
In the above, it is preferred that the sparse part has a dimension (w1) in the longitudinal direction of from 1 to 5 mm.
It is preferred that the sparse part has a depth dimension (d2) from the surface of the dense part toward the absorbent core of from 0.5 to 3 mm.
It is preferred that the sparse parts are arranged with a pitch (p) in the longitudinal direction of from 3 to 15 mm.
Owing to the dimensions, a wearer hardly receives uncomfortable feeling due to the unevenness, and the separation of the surface sheet and the absorbent core can be effectively prevented.
The sparse parts may be staggered in the longitudinal direction, between two adjacent peaks. That is, the sparse parts may be arranged in such a manner that one sparse part formed on one peak is positioned between two sparse parts formed on another peak adjacent thereto in the transverse direction.
The sparse parts may be arranged to surround a prescribed region of the surface sheet.
The sparse parts may be formed as concentrated in a prescribed region of the surface sheet.
In the above, it is also preferred that, in each valley, there is provided at least one connecting part to connect between two adjacent peaks.
Owing to the structure, soft feeling of the surface sheet can be maintained, and the shape thereof can be prevented from losing.